1. Field of the Invention
This invention relates to a pressure gauge and more particularly an to improved system whereby the position of an indexing wheel relative to a pressure-applying wheel can be maintained more reliably in a machine of the kind in which a feed roller is pressed into contact with a workpiece by rotation of the pressure-applying wheel.
2. Description of the Prior Art
An example of such a machine is a laminating machine in which upper and lower feed rollers, which have the function of feeding through the machine a sheet to be laminated together with laminating film, are moved together or apart by the manual rotation of a main wheel. Between the casing of the machine and the main wheel is an indexing wheel which normally rotates with the main wheel but which can be manually rotated relative to the main wheel to bring an indexing mark on the indexing wheel into alignment with a mark on the machine casing. An optimum pressure for a given thickness of the workpiece (sheet to be laminated and laminating film) is found by trial and error and the angular position of the main wheel when this optimum pressure is achieved is registered by aligning the two marks. In subsequent operations with workpieces of the same constitution and thickness the operator ceases to turn the main wheel when the two marks come into alignment.
Hitherto the main and indexing wheels have been pressed into frictional contact by a screw-threaded arrangement. If this is too tight the indexing wheel cannot be rotated manually relative to the main wheel. If it is too loose the indexing wheel will not reliably rotate with the main wheel so that the two marks come into alignment with the main wheel at a different angular position from its previous one. If to overcome this problem the operator first tightens the screw-threaded arrangement to ensure that the indexing wheel rotates with the main wheel, then slackens it to adjust the indexing wheel, then re-tightens it this makes for a laborious operation which wastes the operator's time.